The prior art discloses two different types of activating crimping tools:
a) For a first type of activation, e.g. described in German Patent No. DE 195 07 347 C1 corresponding to U.S. Pat. No. 6,176,116, hand levers are pivoted in a plane of the pliers wherein a leveled head of the pliers as well as the crimping jaws are also located in that plane. The connecting element to be crimped and an electric wire inserted into the connecting element are introduced into a nest built by the crimping jaws. The connecting element and the wire are inserted into the nest in a direction perpendicular to the aforementioned plane. With the movement of the hand levers, the crimping jaws move in the aforementioned plane towards each other and versus the longitudinal axis of the connecting element.
b) According to a second way of activating the crimping tools, e.g. disclosed in German Patent No. DE 40 26 332 C2 corresponding to European Patent No. EP 0 471 977 B1, German Patent No. DE 40 39 435 C1 corresponding to U.S. Pat. No. 5,187,968, or German Patent No. DE 198 18 482 C1 corresponding to U.S. Pat. No. 6,151,950, the hand levers and the leveled head of the pliers also extend in one common plane as for the variant a). However, here the connecting element is not introduced perpendicular to the aforementioned plane into the nest built by the crimping jaws. Instead, the connecting element is introduced into the front surface of the head of the pliers, wherein the longitudinal axis of the connecting element as well as the direction of introduction of the connecting element into the nest built by the crimping jaws lies in the aforementioned plane. The longitudinal axis of the nest and of the connecting element housed in the nest is aligned with the middle axis of the two hand levers.
Due to the different mechanisms used for transferring and converting the force between the hand levers and the crimping jaws for crimping pliers according to variant a), a plurality of crimping jaws has to be used, wherein in particular the number of the crimping jaws coincides with the number of the corners of the cross-section of the connecting element at the end of the crimping process. Instead in the transfer mechanism for the force used for pliers according to variant b), only two crimping jaws are used, wherein for such variant each crimping jaw (or a die connected with each of the crimping jaws) determines a plurality of contour lines of the contour formed in the connecting element at the end of the crimping process. In general, for variant b) one crimping jaw or die determines a half-contour of the crimping contour. Often crimping pliers according to variant b) use a trapezoidal contour of the crimping surfaces of the crimping jaws or dies.
A crimping tool with a pistol-shaped design is known from U.S. Pat. No. 3,201,969. The housing comprises an L-shaped angled handle having an activation element similar to the trigger of a pistol. Via the activation element, a valve might be switched such that a pneumatic pressure is fed to a piston. The activated piston is moves in axial direction. Such axial movement is converted by a toggle mechanism into a radial crimping movement of crimping elements. These crimping elements radially crimp a work piece introduced into the nest of the crimping tool located at the muzzle of the pistol. U.S. Pat. No. 3,201,969 also mentions an embodiment, wherein the crimping movement is manually caused by a finger pressing an activation element instead of the aforementioned pneumatic activation. However, U.S. Pat. No. 3,201,969 does not explain how to provide the necessary large crimping forces for manual activation with one single finger.
German Patents Nos. DE 42 41 224 C1, DE 41 01 284 C2 and U.S. Pat. No. 6,173,466 B1 also disclose crimping tools having a pistol-like design. However, for the embodiments disclosed in these patents, the crimped work piece is introduced transverse to the muzzle of the pistol-like tool.
U.S. Pat. No. 4,720,911 relates to a tool with a design similar to a tool for rivets. Such tool does not produce a crimping force biasing a work piece in radial direction but produces an axial compression force.
Further prior art is known from German Patents Nos. DE 101 40 270 B4 and DE 42 41 971 C1, and Swiss Patent No. CH 402 099 corresponding to U.S. Pat. No. 3,156,139 and U.S. Pat. No 3,126,750.